Boilers are commonly used in hydronic or other heating systems in residential, institutional, and commercial buildings, as well as in other applications. Typically, in a boiler system, a fuel burner produces heat that is transferred via a heat exchanger to water, which is circulated to transport the heat to end-use locations. In some cases, damage or injury may result if the boiler is fired when the water level is low, if a water valve is stuck, if a water circulation pump fails and/or if some other irregularity in operation or maintenance occurs. Some boiler systems include a low water sensing mechanism, such as a probe or float to monitor the water level in the boiler. Such a sensing mechanism generally requires additional inputs to the boiler controller, wiring to connect the sensor and controller, and in some cases, an additional hole or holes in the heat exchanger for the sensor. Some boiler systems include additional sensors to detect when a water valve might be stuck, when a water circulation pump fails and/or if some other irregularity occurs. All of this, however, can add significant complexity and cost to the system, and in some cases, may introduce additional vulnerabilities to the system.